Registration Review Ecological Risk Assessment Problem Formulation for the Nematicide Fosthiazate 3/3/2009

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## R EGISTRATION 

## R EVIEW



## E COLOGICAL 

## R ISK 

## A SSESSMENT



## P ROBLEM 

## F ORMULATION FOR 

## :



## F OSTHIAZATE

O- ETHYL 

### -S-(1- METHYLPROPYL 

### )(2- OXO 

### -3- THIAZOLIDINYL 

### )-

PHOSPHONOTHIOATE

CAS# 98886-44-3; PC Code 129022

P REPARED B Y :

Keara Moore, Chemist
Environmental Risk Branch 3
Environmental Fate and Effects Division Office of Pesticide Programs

A PPROVED B Y :

Dana Spatz, Branch Chief
Environmental Risk Branch 3
Environmental Fate and Effects Division Office of Pesticide ProgramsRegistration Review Ecological Risk Assessment Problem Formulation for the Nematicide Fosthiazate 3/3/2009

- 2 - 1. S TRESSOR S OURCE AND D ISTRIBUTION

Fosthiazate is used for contro l of a broad spectrum of nemato de species in tomatoes and also suppresses insects including sweet pot ato whitefly, tomato pinworm, and beet armyworm. It is an organophosphate inse cticide which exerts toxic action through inhibition of acetylcholinesterase, an enzyme that is necessary for normal nerve function.

Current labels allow applicati on of fosthiazate at a maximu m annual rate of 1.5 lb active ingredient/A. It must be applied through drip irrigation systems placed under a plastic mulch. Registered formulations of fosthia zate include the techni cal product (Reg. No. 71512-6) as well as three end use produc ts (Fosthiazate 900E C, Reg. No. 71512-4; Nematachide 500EC, Reg. No. 71512-5; and Fosthiazate 75% EC, Reg. No. 71512-17).

All labels are time-limited and are sche duled to be terminated March 30, 2009.

2. I NTEGRATION OF A VAILABLE I NFORMATION

The risk assessments available in the docket, and which serve as the basis for this problem formulation, include the following:

• New Chemical Section 3 assessment (December 9, 2002), including Amendment (February 27, 2003) and Amendment II (July 10, 2003)

• Organophosphate Cumulative Risk A ssessment – 2006 Update (August, 2006)

• Review of Environmental Fate Asse ssment for Fosthiazate Groundwater/ Drinking Water Modeling Estimates (February 26, 2008)

3. E COLOGICAL E FFECTS

T OXICITY S TUDIES

Acute toxicity

The available acute toxicity da ta on the active ingredient indicate that fosthiazate is highly toxic to birds (LD 50 = 16.6 mg/kg; LC 50 = 85 ppm), moderately toxic to small mammals (LD 50 = 51 mg/kg, female rat), practically non toxic to freshwater fish (LC 50 = 111 ppm–157 ppm), highly toxic to freshwater invertebrates (EC 50 = 0.26 ppm), slightly toxic to estuarine/marine fish (LC 50 = 40.6 ppm), and highly to very highly toxic to estuarine/marine invertebrates (EC 50 = 0.43 ppm-14.1 ppm).

Chronic toxicity; aquatic animals

Chronic effects in the freshwater fish early life stage using the fathead minnow ( Pimephales promelas ) included reduced dry weight a nd length of young fish (NOAEC = 2.32 ppm, LOAEC 4.48 ppm). The freshwater inve rtebrate life-cycle study determinedRegistration Review Ecological Risk Assessment Problem Formulation for the Nematicide Fosthiazate 3/3/2009

- 3 - an NOAEC of 0.061 ppm and an LOAEC of 0.128 ppm based on reduced number of offspring produced and parental mortality. No chronic toxicity da ta are available for

estuarine/marine fish or invertebrates.

Chronic toxicity; terrestrial animals

Both the mallard duck and bobwhite quail avian reproduction studies had the same NOAEC (21.7 ppm) and LOAEC (42.6 ppm). Significant effects on male and female weight gain, decreased eggshell thickness and increased cracked eggs were observed in the bobwhite quail. A 2 generation rat st udy yielded a reproductive NOAEL of 10 ppm (or 0.91 and 0.91 mg/kg/day for males and fe males respectively) and a LOAEL of 30 ppm (equivalent to 2.09 and 2.60 mg/kg/day males and females, respectively) based on decreased viability index, litte r size and pup weight for the f 1 generation.

Toxicity to plants

An extensive battery of Tier I and Tier II terrestrial plant to xicity tests were performed on technical fosthiazate in which dicots appear to be more sensitive than monocots. Based on a Tier II seedling emergence test on technical fosthiazate, the NOAEC and EC 25 for mustard are 0.8 and 1.0 lb ai/A respectively. Although the Tier I test results showed peppers were more sensitive (27 %) than mu stard (<25 %) no test was conducted with peppers. For Tier II vegetative vigor, the most sensitive terrestrial plant is the dicot buckwheat (NOAEC = 0.8 lbs ai/A; EC 25 = 3.3 lbs ai/A). Sorghum was the only monocot tested (NOAEC = 3.0 lbs ai/A and the EC 50 = > 6.0 lbs ai/A).

No acute risk LOCs were exceeded for non-vascular plants based on a Tier I test with the green alga ( Selenastrum capricornatum ) which found no adverse effects at a concentration equal to 4.5 ppm. Ther e were no data for vascular plants.

Toxicity to terrestrial invertebrates

The acute contact honey bee LD50 is 0.247 u g/bee (MRID 41347636). Since the LD50

is less than 2 ug per bee fosthiazate TGAI is categoriz ed as highly toxic to pollinators on

an acute contact ba sis. (MRID 41347636).

I NCIDENT R EPORTS

The Agency has no incident reports in the Ec ological Incident Information System (EIIS) for adverse effects to fish, wild life, or plants that were attributed to fosthiazate use. However, the lack of reported incidents may be due to the fact that there is currently no actual usage of fosthiazate (see Sec tion 6), rather than to low risk.Registration Review Ecological Risk Assessment Problem Formulation for the Nematicide Fosthiazate 3/3/2009

- 4 - 4. E XPOSURE C HARACTERISTICS

In the terrestrial environment, laboratory studie s suggest that persiste nce of fosthiazate in

soils will be on the scale of w eeks to months, with rates depending on soil pH. In aerobic soils, measured half-lives were 14.0 to 57.7 days with significantly slower metabolism in acidic soils (t 1/2 = 41.8 to 57.7 days) than in alkaline soils (t 1/2 =14.0 to 20.7 days). Substantial degradation was seen in sterile c ontrols as well, suggesting that some of the transformation occurs through ab iotic processes. Fosthiazat e has low sorpti on to soil and,

based on K

oc values ranging from 25 to 285.7 mL/g

oc , is classified as mobile to moderately mobile by the FAO classification scheme.

The persistence and mobility of fosthiaza te are conducive to runoff, but currently approved application methods are designed to minimize potential transport to surface water. Labels require applic ation through drip irrigation unde r plastic mulch. Therefore, spray drift to surface water is not a concern, and the potentia l for runoff is reduced by the direct soil application and by the protection fr om precipitation. If fosthiazate does reach aquatic environments, it is st able to aquatic pho tolysis and has limited hydrolysis in neutral and acidic conditions, but it hydrolyzes rapidly in alkaline conditions. It is moderately persistent in water-sediment syst ems, with an average half-life in aerobic environments of 32 days and in an aerobic environments of 41 days.

Terrestrial field dissipation (TFD) studies we re conducted with 4 lb s a.i./A applied to bare ground and incorporated 4 to 5 inches with no plastic mulch. In three sites, measured half-lives were 9 to 17 days, and in a fourth site, the half -life was 28 days. All studies were conducted in acidic soils (p H <6.4), where the le aching potential of fosthiazate is expected to be the highest. In most cases, residues were detected to no more than 15-30 cm below the soil surface, but in three of eight tests, residues were found at low levels up to 46 cm below the soil surface.

In the currently registered use, the plas tic mulch cover would minimize volatilization and runoff, therefore increasing the amount of the chemical available for leaching. However, with the drip irriga tion method, a small amount of water is slowly dripped into soils precisely where it is needed, thus lessening the amount of water flowing down through the soil past the root zone where it cannot be used by the crop. This should greatly reduce the potentia l for the chemical to reach ground water systems.

As summarized in Table 1, carbon dioxide and bound residues we re the primary end products in most cases. Additionally, six ma jor degradates were detected along with unidentified organic vola tiles. Study lengths were not suffi cient to determine the pattern of formation and decline for all degradates. The only degradates found in terrestrial field dissipation studies were MBSo /MBSx and BSA, at maximum amounts of 1 to 4% of the applied.Registration Review Ecological Risk Assessment Problem Formulation for the Nematicide Fosthiazate 3/3/2009

- 5 - Table 1. Major degradates of fosthiazate, as a percentage of the parent applied.

Study Type (Study Length) a

Hydrolysis Degradates b

pH 5 (30 d) pH 7 (30 d) pH 9 (14 d) Aerobic

Soil (150 d) Aerobic Aquatic (140 d) Anaerobic Aquatic Soil (120 d)

DETO ~13 % ~13 % up to 10% c minor

DBTO 45%

TZO 40% 32% (60 d)

DTTO 44% up to 10% c minor

MBSo/

MBSx d 11% (28 – 35 d) 16.4% (60 d)

BSA 20%

Unid'd organic

volatile ~30% 8%

a Unless otherwise noted, maximum concentrat ions occurred at study termination.

b DETO : (RS)-S-sec-butyl hydrogen 2-oxo-1, 3-thiazolidin-3-ylphosphorothioate; DTTO : (RS)-S-sec-butyl O-ethyl hydrogen phosphorothioate; MBSo : sec-butyl methyl sulfone; MBSx : sec-butyl methyl sulfoxide; BSA : 2-

butanesulfonic acid.

c Aerobic aquatic study di d not separate DETO/DTTO.

d MBSo/MBSx not separated.

5. C LEAN W ATER A CT

Fosthiazate is not identified as a cause of impairment for any water bodies listed as impaired under section 303(d) of the Clean Water Act, based on information provided at http://oaspub.epa.gov/tmdl/waters_ list.impairments?p_impid=3

.

The Agency invites submission of water quality data for this pesticide. To the extent possible, data should conform to the quali ty standards in Appendix A of the OPP Standard Operating Procedur e: Inclusion of Impaired Water Body and Other Water Quality Data in OPP’s Registration Review Risk Assessment and Management Process (see: http://www.epa.gov/oppfead1/cb/ ppdc/2006/november06/session1-sop.pdf ), in order to ensure they can be used quantit atively or qualitatively in pesticide risk

assessments.

6. C HARACTERISTICS OF E COSYSTEMS P OTENTIALLY AT R ISK

For fosthiazate and pesticides in general, the ecosystems at greatest risk are those in close proximity to the use areas. These woul d include agricultural fields (surrounding nonagricultural terrestrial habitats) and water bodies directly adjacent to treated fields that may receive chemical residues via drift, vol atilization, and/or r unoff. Within water bodies, the water column, sediments, and pore wa ter are all compartments of concern.Registration Review Ecological Risk Assessment Problem Formulation for the Nematicide Fosthiazate 3/3/2009

- 6 - Fosthiazate is registered for use on tomatoes only. According to data from the United States Department of Agriculture’s Nati onal Agriculture Statistics Service (USDANASS) pesticide usage data from 2007 and 2008 1 , tomatoes are grown primarily in California (78% total national acreage) and Florida (9%). However, the Screening Level Usage Analysis (SLUA) done by the Biol ogical and Economic Analysis Division (BEAD) found no use data for fosthiazat e (Use Report Package Memo; October 28, 2008). This is based on data from the Screen ing Level Usage Analysis (SLUA) database, which is a compilation of NASS (National Agri cultural Statistics Survey) and proprietary data from 2001-2007, and the California Depa rtment of Pesticide Regulation (CDPR)

database was checked as well.

7. A SSESSMENT E NDPOINTS

Assessment endpoints are defined as “explicit expressions of the ac tual environmental value that is to be protected.” Defining an assessment endpoint involves two steps: 1) identifying the valued attributes of the envir onment that are considered to be at risk; and 2) operationally defining the assessment endpoint in terms of an ecolo gical entity (i.e., a community of fish and aquatic invertebrate s) and its attributes (i.e., survival and reproduction). Therefore, selection of th e assessment endpoints is based on valued entities (i.e., ecological recep tors), the ecosystems potential ly at risk, the migration pathways of pesticides, and the routes by which ecological receptors are exposed to pesticide-related contamination. The selecti on of clearly defined assessment endpoints is important because they provide direction a nd boundaries in the ri sk assessment for addressing risk management issues of c oncern. Changes to assessment endpoints are typically estimated from the available toxicity studies, which are used as the measures of effects to characterize potentia l ecological risks associated w ith exposure to a pesticide,

such as fosthiazate.

To estimate exposure concentra tions, the ecological risk asse ssment considers application at the maximum application rate to fields th at have vulnerable soils. The most sensitive toxicity endpoints are used from surrogate test species to estimate treatment-related direct effects on acute mortality and chronic repr oductive, growth and survival assessment endpoints. Toxicity tests are intended to determine effects of pesticide exposure on birds, mammals, fish, terrestrial and aquatic invertebra tes, and plants. Thes e tests include shortterm acute, sub-acute, and reproduction studi es and are typically arranged in a hierarchical or tiered system that progresse s from basic laboratory tests to applied field studies. The toxicity studies are used to ev aluate the potential of a pesticide to cause adverse effects, to determine whether further testing is required, and to determine the need for precautionary label statements to minimize the potential adverse effects to nontarget animals and plants.

Fosthiazate is classified as highly toxic to birds and modera tely toxic to mammals on an acute oral basis. It is also highly toxic to aquatic invertebrates and honeybees on an acute basis, but it is only slightly toxi c to fish. Chronic toxicity da ta that are available for these

1 http://www.nass.usda. gov/QuickStats/indexbysubject.jsp?Text1=&s ite=NASS_MAIN&select=S elect+a+State&Pass_ name=&Pass_group=Crops+%26+P lants&Pass_subgroup= Vegetables. Accessed 2/26/2009.Registration Review Ecological Risk Assessment Problem Formulation for the Nematicide Fosthiazate 3/3/2009

- 7 - taxa indicate that chronic effects may be of concern for exposed animals that do not experience acute lethality.

8. C ONCEPTUAL M ODEL

In order for a chemical to pose an ecologica l risk, it must reach ecological receptors in biologically significant concen trations. An exposure pathway is the means by which a pesticide moves in the environment from a source to an ecological receptor. For an ecological exposure pathway to be complete, it must have a source, a release mechanism, an environmental transport medium, a point of exposure for ecologi cal receptors, and a feasible route of exposure.

The conceptual model ( Figure 1 ) depicts the potential path ways for ecological risk

associated with fosthiazate use. The c onceptual model provides an overview of the expected exposure routes for organisms within the fosthiazate action area. For terrestrial organisms, the major route of exposure consid ered is the dietary route; consumption of

food items such as seeds or insects that have fosthiazate residues as a result of contact in

the soil. Foliar residues ar e not expected because there ar e no spray applications. For aquatic animal species, the major routes of exposure are consider ed to be via the respiratory surface (gills) or the integument. Direct contact and/or root uptake is the major route of exposure for terrestrial and we tland (riparian) plants, while aquatic plants may be exposed via direct uptake and adsorp tion. Estimated exposure concentrations for all organisms are obtained through the us e of several Agency exposure models.

R ISK H YPOTHESIS

Based on an examination of the physical/chemi cal properties of fosthiazate, the fate and disposition in the environm ent, and mode of applica tion, a conceptual model was developed that represents the possible rela tionships between the stressor, ecological receptors, and the assessment endpoints.Registration Review Ecological Risk Assessment Problem Formulation for the Nematicide Fosthiazate 3/3/2009

- 8 - Stressor Fosthiazate, applied through drip irrigation under plastic mulch

Source/ Transport Pathways Direct Deposition Runoff/

Erosion Leaching (infiltration/ percolation)

Source/ Exposure

Media Terrestrial Food

Residues in soil (seeds, insects) Upland Foliage/Soil Riparian/

Wetland Foliage/Soil Water
Column/

Sediment Groundwater

Exposure

Point Ingestion Direct contact Direct contact Gill/ Integument Uptake

Receptors

Attribute Changes Terrestrial Vertebrates Birds, Small Mammals, Reptiles, Terrestrial

Insects Terrestrial Upland

Plants

Individual Animals

Reduced survival Reduced growth Reduced reproduction Aquatic Invertebrates Aquatic Vertebrates Amphibians Aquatic Plants Wetland/ Riparian

Plants

Individual Plants

Seedling emergence Vegetative vigor Individual

Vertebrates and

Invertebrates

Reduced

survival

Reduced growth

Reduced reproduction Food Web Exposure (biconcentration)

Piscivourous

Vertebrates Birds,

Mammals

Individual

Animals

Reduced survival, growth, and reproduction Plant Population

Reduced population growth

Figure 1. Conceptual model for potential effects of fosthiazate application to nontarget aquatic and terrestrial organisms.

9. A NALYSIS P LAN O PTIONS

In Registration Review, pesticide ecological risk assessments will follow the Agency’s Guidelines for Ecological Risk Assessment, will be in compliance with the paper titled “Overview of the Ecological Risk Assessm ent Process in the Office of Pesticide Programs, U.S. Environmental Protection Ag ency” (“Overview Document”) (January 2004), and will be done in accordance with Se ction 7 of the Endangered Species Act.

E COLOGICAL R ISK A SSESSMENT

Previously completed screening level ecologi cal risk assessments for application of fosthiazate at 1.5 lb a.i./A through drip irriga tion under plastic mulch have found that this use poses minimal acute or chronic risk to endangered and non- endangered non-target plants and animals. Therefore, no additional analysis to refine conclusions will be necessary for registration review.

Due to the application method, aquatic e xposure will be low a nd risk to aquatic organisms is minimal. In the new chemical assessment, uses of fosthiazate at twice the currently labeled rate applied through broad cast spray did not exceed any aquatic levelsRegistration Review Ecological Risk Assessment Problem Formulation for the Nematicide Fosthiazate 3/3/2009

- 9 - of concern. With the drip irrigation met hod required by current labels, drift to surface water is not a factor, and because fosthiazate is applied directly to soil in low amounts of water and is protected from precipitation by the plastic mulch, runoff is unlikely. Therefore, previous assessments concluded that any aquatic exposure from the current use on tomatoes will be substantially lower than in those estimated for other uses and so

there will still be no exceedances.

In the terrestrial environment, there is so me potential for dietary exposure to birds and mammals who probe beneath the surface for seeds and insects or which feed on emerging seedlings containing translocated residues. This exposure is unquantifiable and expected to be negligible, so there is minimal risk to terrestrial organisms as well.

For all use patterns applied by spray met hods, the previous assessment found that fosthiazate would pose acute risk to birds, mammals and pollinators such as honey bees

as well as chronic risk to bi rds and mammals. It would pose acute and chronic risk to endangered birds and mammals as well as acut e risk to endangered insects. Acute or

chronic risk LOCs were not exceeded fo r non-endangered and endangered freshwater fish, marine/estuarine fish or invertebrates, or to aqua tic plants. At the highest application rates, fosthiazate exceeded the LO C for acute risk to endangered freshwater aquatic invertebrates. Because these sp ray uses are no longer supported, additional analysis to refine these conclusions will not be necessary.

Although the Agency anticipates that no quantit ative ecological risk assessment will be needed, a qualitative endangered species asse ssment will be conducted for this fosthiazate

use.

D RINKING W ATER A SSESSMENT

The most recent drinking water assessment considered exposure from the currently labeled use on tomatoes using drip irri gation under plastic mulch (Review of

Environmental Fate Assessment for Fosthi azate Groundwater/ Drinking Water Modeling Estimates; February 26, 2008). Estimated dri nking water concentrations in ground water were modeled using the most up to date version of SCI-GROW (v2.3, Jul. 29, 2003) and the most recent data. Therefore, no refi nement is necessary unless requested by the

Health Effects Division.

That assessment found exposure to fosthiaza te in drinking water from surface water sources to be unlikely due to the applica tion method. In ground water, the estimated drinking water concentration was 1.8 ug/L. Th ere is some uncertain ty in this result because the model does not account for the drip irrigation application method or for the plastic mulch. Drip irrigation is likely to lead to lower exposure because the low amount of water used would limit leaching. However, additional uncertainty results from the pH dependence of fosthiazate fate behavior. Th e modeled results are based on sorption and persistence data that represent the average of all soils, while there may be more leaching and higher exposure in acidic soils wh ere fosthiazate is more persistent.Registration Review Ecological Risk Assessment Problem Formulation for the Nematicide Fosthiazate 3/3/2009

- 10 - A NTICIPATED D ATA N EEDS

The Agency does not foresee requiring any addi tional ecological eff ects or environmental

fate studies listed in 40 CFR Part 158 in or der to complete regist ration review for the currently registered use on tomatoes using drip irrigation. Although the new chemical assessment identifies data gaps, those gaps are only relevant to uses that are no longer supported, and the assessment concludes that for the drip irrigation method, all fate and ecotoxicity requirements have been met. B ecause no additional analysis is needed to refine risk conclusions from the currently registered us, no additional data are needed. No search of open literature will be conducted.